1. Field of the Invention
The present invention relates generally to conveyors and, more particularly, to a lift and carry accumulating conveyor.
2. Description of the Prior Art
Lift and carry conveyors for transporting various types of parts along a conveyor line are well known. Lift and carry conveyors, such as disclosed in U.S. Pat. No. 4,838,411 to Rainey et al typically comprise a pair of spaced apart and parallel stationary rails as well as at least one movable rail which extends generally parallel to the stationary rails. The movable rail is movable both between a forward and a retracted position as well as between an upper and a lower position. Thus, in order to convey parts supported by the stationary rails along the conveyor line the movable rail, when in its retracted or lower position, is first moved to an upper position thus lifting the parts up from the stationary rails. The movable rail is then moved to the forward position and, thereafter, to the lower position. When the movable rail is moved to the lower position, the parts are again placed upon the stationary rail so the parts are effectively transported along the conveyor line by the distance equal to the stroke of the movable rail between its forward and retracted position. The movable rail is then moved to its lower retracted position and the above cycle is repeated.
The production of the stationary rails for lift and carry conveyor systems is generally quite complex and expensive. The rails are fabricated out of several pieces of metal which are welded together. Assembly of the conveyor system requires extensive machining of the rails to produce bores and apertures for mounting the rails. In addition, the rails must frequently be adapted for mounting of support accessories such as limit switches, sensors, covers and the like. It has been the practice to individually measure mounting holes in the conveyor rails for these accessories when fabricating the conveyor rails for a particular conveyor system. Such a procedure, however, is time consuming and thus, increases the overall labor cost of the conveyor system.
Likewise, the movable rails must be precisely formed and positioned in order to properly engage the part to be moved without damaging the part. Slight changes in the size and shape of the parts may require the fabrication of new rails in order to provide properly formed and positioned surfaces for engaging the part. The production of new rails is quite expensive and replacement of the rails can be quite time consuming.